Plastic materials used in the manufacture of powder coatings are classified broadly as either thermosetting or thermoplastic. In the application of thermoplastic powder coatings, heat is applied to the coating on the substrate to melt the particles of the powder coating and thereby permit the particles to flow together and form a smooth coating.
Thermosetting coatings, when compared to coatings derived from thermoplastic compositions, generally are tougher, more resistant to solvents and detergents, have better adhesion to metal substrates and do not soften when exposed to elevated temperatures.
Resins which exhibit good weatherability and meet the basic Tg (glass transition temperature) requirements for powder coating compositions are becoming increasingly important, particularly for outdoor applications.
Powder coatings based on acrylic resins are known to have excellent weathering performance but are generally more expensive.
British Patent No. 962,913 discloses polyesters containing cyclohexanedicarboxylic acid (CHDA) and 2,6-decalindimethanol useful as film and molding plastics.
U.S. Pat. No. 3,313,777 discloses polyesters containing CHDA and 2,2,4,4-tetramethyl-1,3-cyclobutanediol useful as film and molding plastics.
U.S. Pat. No. 4,363,908 discloses copolyesters containing CHDA and 2,2,4,4-tetramethyl-1,3-cyclobutanediol useful as adhesives.
U.S. Pat. No. 4,525,504 discloses stabilized polyesters with improved weatherability based on CHDA and 2,2,4,4-tetramethyl-1,3-cyclobutanediol. These polyesters are high molecular weight polyesters useful in molding plastics.
U.S. Pat. No. 5,097,006 discloses all-aliphatic polyester resins based on 1,4-cyclohexanedicarboxylic acid and hydrogenated bisphenol A and/or cycloaliphatic diols, useful as weatherable powder coating resins.
Powder coatings which exhibit good weatherability and meet the basic Tg (glass transition temperature) requirements for a thermosetting powder coating composition are becoming increasingly important, particularly for outdoor applications. We have found that polyester resins based on dimethyl 2,6-decalindicarboxylate and neopentyl glycol meet the basic Tg requirement for powder coatings and can be formulated with a crosslinker into powder coatings having excellent weatherability.